Transformer spark plug



Jan. 25, 1949.

A. C. WALL.

TRANSFORMER SPARK PLUG Original Filed Aug. 12, 1944 v INVENTOR fllexander 6 71 211;

ATTORNEY Patented Jan. 25, 1949 UNITED STATES PATENT OFFICE 2,459,856 TRANSFORMER SPARK PLUG Alexander C. Wall, Indianapolis, Ind, assignor to P. It. Mallory & 00., 1110., Indianapolis, Ind., a corporation or Delaware Original application August 12, 1944, Serial No.

549,278.. Divided and this application Novem- V ber 16, 1945, Serial No Claims. (Cl. 315-57) The present invention relates to a combination This application is a division of my copending sembly associated with a portion of a high heapplication, Serial No. 549,2'ze entitled Ignition system and apparatus thereof.

A general object of the present invention is the provision of such a device which is compact and self-contained, easily constructed, sturdy, readily replaceable, accurate and efiicient in operation moisture-proof, adapted for efiicient operation under widely varying conditions oi use, readily utilized in conventional structures with a minimum of alteration procedures, employable in a simple manner with associated structure to complete portions of circuits of an ignition system while efiectively cooperating with said associated structure to provide complete and eiiective shielding thereby minimizing radiation of radio interference energy, and in which the parts are so arranged and assembled as to minimize energy losses.

A more specific object of the invention is the provision of a readily replaceable transformerspark plug assembly which is adapted for a wide variety of circuit applications where ability to withstand mechanical vibrations, high voltage stresses and high temperatures is necessary or desirable.

A still more specific object of the invention is the provision of a transformer-spark plug assembly which assures freedom from flash-over, maxicoupling efficiency, minimization of corona efiect and attendant energy loss, and immunity from danger of break-down under the high temperatures of engine operation.

Other objects of the invention will be apparent from the following description and accompanying drawings taken in connection with the appended claims. 7 e p The invention accordingly comprises the features of construction, combination of elements, arrangement of parts, and methods of manufacture referred. to above or which will-be brought out and exemplified in the disclosure hereinafter set forth, including the illustrations in the drawings, the scope of the invention being indicated in the appended claims.

In the drawings:

Figure 1 is a schematic diagram of a typical ignition circuit for use with the transformerplug unit of the present invention;

Figure 2 is a sectional view, with parts broken away, of the novel transformer-spark plug asquency ignition system;

FigureB isa detail View, having parts broken away andomitted, of the unit shown in Figure V with the parts in disassembled relation;

Figure 4 is a longitudinal sectional View of. a

modified form of the primary winding structure shown in Figures2 and 3;

Figure 5 is a view similar to Figure 2, but with additional parts broken, away and omitted, of a modified form of the structure; and

Figure 6 is an elevational view, 'th parts broken away and omitted and with the secondary winding structure in longitudinal section, of a modification of the structure shown in Figure 5. .Whilea preferredembodiment oi the invention is described herein, it is contemplated that considerable variation may. be made in the method of procedure and the construction of parts without. departingfrom the spirit of the invention. In the following description and in the claims, parts will be identified byspecific names for convenience, but they are intended to be as generic in their application to similar parts as the art will permit.

In accordance with this invention, a combination spark plug-transformer unit isprovided in which the transformer is seated in a chamber formed at the upper portionof the spark plug. The high tension end of the secondary winding is originally. attached to a conedioil which is pressed andifiattened against the,- contactafor the central spark plug electrode during assembly of the unit while the low tension end of the secondary is positively groundedtov the spark plug casing. The primary winding ispreferably mountedupon a connecting cable of a high;fre-- quency ignition system, this cable being attached and sealed to the upper portion of the spark plugzin anovel manner to secure the primary winding firmly in closely coupled relation to the secondary winding and to permit impregnation of the unit to exclude air or gases fromthe interior thereof whereby corona efiect is eliminated or substantially minimized. A glass cup formed from a suitable insulating material may be interposed between the primary and secondary windings witl'rthe base of the cup adjacent the high tension endof the secondary winding. In this manner, arcing or flash-over difficulties due to the. high-voltage gradient at the high tension end are eliminated without the necessity of providing anextended insulating portion projecting a; substantial distance beyond the end of the transformer. y

It is a feature of the invention that the casing of the spark plug effectively shields the transformer together with the associated leads and circuit components, the casing cooperating, in a novel manner, with the shielding cable and connection therefor to suppress radio noise disturbances resulting fromthe high frequency ignition circuits.

As pointed out in my copending application Serial No. 549,278, fiiled August 12, 1944, for "Ignition system and apparatus thereof, the transformer of the present invention is adapted for use in an ignition system for" internal combustion engines which periodically generates pulses of electrical energy, distributes these pulses toward the spark plugs of the'various cylinders, then converts the: energy of the pulses to a high frequency current and finally steps up the voltage of said high frequency current for supply to the spark pluggaps thus overcom- -mg firingdifiiculties-causedl by fouling of spark plug electrodes with carbon and oil.

c apparatus may be incorporated in an'ignition-harness similar in many respects to those with which radial airplane engines are now equipped. Each engine; cylinder, the wall of one ot which is"indicated a ;t ill in 'liigure 1, may be equipped for dualign-ition and accordingly may have mounted inside walls'thereof a pair of transformerspark plug units, one of which is diagram- DQQtlCaLIYJIIGiCatGd'2115f, to each of which is connected a supply cablel2, in turn connected to an'ignition manifoldindicated atl3. The ignitiongnanifold maybe similar to that now used i ignition harnesses for other types of ignition "s terns-and; asfsuch, may bean encasing and sli ieldingfstijucture' in w ichare located a plurality-of supply conductors each of which is anchored to coupling means mounted on the manifdld'for connecting that conductor to the spark "plug supply cable IZ. The coupling means in c ides ae'onvert i' pa whichlis diagrammatically zippered-n l4 ini-Figiure 1. V 1

showii in Figure 1,"a typical circuitof an ch; the trahsformen of the ignition systenuin wh i u 7 l be employed to advantage,

15 or means for generatpresent'inveiition 'may energy such, for example,

ma' onprise a source ingpulses' of'ele'ctrical' are standard magneto which may comprise a pnmaiyccirls; a secondary coil l1 andibreaker mechanism |8'including' an" operating cam" l3. One'side of the secondary-coil H of the magneto I may; as shown; beco'n'necte'd by a'conductor '20 to the'rotaify' element 2| of a" distributor unit '2 2j'whicli rotary element is adapted successively 'to'eoppe ate tv'ith a plurality of fixed distributor terminals 23-23. Each ofa'plurality of conduc tors 2lis'co'nnecte'd to one of the distributor terminals23 to fermpne side of 'asupply' circuit 'tof one of the transformerspark plug units l l. Theother's'ide of the supply circuit is provided by a groundin ccniiednon 25"for the secondarycoil 1'7, suchas through the case of the magneto l5 to'the engine frame, and the manifold I3 is also grounded, preferably to the engine frame. The converter unit' l4 comprises a metallic casing 2E connected to the manifold l3 at'21 and grounded thereby, the casing 26 in turn being connectedat 28 to=0neend of a shielding sheath 29 provided for the cable l2. The sheath 29 is connected at 30110 the shell or 'metallic'oasing 3! of the transformer spark plug unit "I I which'i's'groundedto the cylinder wall l0 and, ina -known manner," carries one or more spark plug electrodes 32-32.

other end of the shielding The supply conductor 24 is connected at 33, as by a socket coupling, to a conductor 34 within the converter unit M. A condenser 35 bridges the conductor 34 and the metallic casing 26. The conductor 34 is also connected to one electrode of spark gap means 36, the other electrode of which is connected to a circuit connector 31, which may also be a socket coupling. A cable conductor 38 is connected between the socket coupling 31 and one end of the primary Winding 3 9 of the novel transformer, the other end of the primary being connected by a cable conductor 40 tothe grounded side of the circuit, such as to the'shielding sheath 29, preferably at or near the connection 28.

Corona eifect tends to occur in gaseous media adjacent elements carrying current at high voltages and particularly at high altitudes where rarefaction becomes appreciable, resulting in serious powerlosses attended by decreased efliclency. In acoordancewith the present invention, this prob lem is efficiently overcome by excluding air or gases fromthe interior of the transformer-spark plug unit by saturation or impregnation with insulating compounds which will withstand the high temperatures adjacent the engine cylinders, such, for example as a fluid polymerizing resin which w 'l be transformed by heat into a heat-stable 301mm semisolid. I Such material, if desired, maybefilled with particle of refractory material such as ground glass, asbestos, mica, or the like. If the mechanical structure assures hermetic sealingof the parts within the encasing shell, heat-stable fluids known in the industry as HDow-Corning Compound, Sa li-Resin, and

ZOOFIuid are satisfactory for impregnating the interior of the spark plug unit.

riiaspark plug ll, Figures 2 and 5, is partially ofconve'ntional construction and, prior to adaptago tio'n to the disclosed ignition system, may comprise ametallicbasing or shell 3! lined with a sleeve lTof'suitableinsulating material, such as a heat-stable ceramic or porcelain, which cooperates" with'affelement 18 of similar material supporting tlierntral electrode 44, the latter being exposed at "the bottom of an interior chamber 80 of the spark plug. In the conventional construct'iOmt-he chamber 80 is provided for receptioh' of"a circuit lconnector unit which, in accordance with the present invention, is replaced by a transformer. The'metallic casing or shell 3| is threaded as at'8l for insertion into a passage formed in the wall it! of an engine cylinder and the connecting cable l2 may be detachably-secured to a'threaded portion 82 of the casing.

'll'ietransformer secondary winding 4! is preferably wound about the exterior of a substantially cylindrical elongated cup or vial 83 of suitable'insulating material, preferably glass, having the minimum wall'thickness necessary for effective insulation of the transformer windings. In this manner, close coupling is afforded between the transformer'windings while still obtaining adequate insulation. For efficient operation, the

distance between the primary and secondary windings should be quite small compared to the distancebetween the secondary winding and the metallic casing 3| of the spark plug. The vial 83 preferably is made from Pyrex glass but other glass materials such as lead glass may be employed provided thin layers thereof are capable of withstanding the high temperatures and voltages towhich they are subjected in operation of the system,- iniwhich voltage stresses of the order of 2,000 -t'd'3j000 volts per mil are'common and local- 'ized: stresses may at times be as high as about 10,006 voltsper mil.

The secondary winding All is arranged upon the glass cup 83 with the low tension end 52 located adjacent the rim of the cup and the hightension end 43' located adjacent thebottom of the cup. P1'eferably, the low tension end. is anchored directly to the rim or the cup by a body or smear $4 ofmetallic material, such as. a silver compo nd, whichmay be adhered to the glass by firing and which is preferably tinned with solder to anchor the wire. The high tension end 43 is preferably anchored to the bottom of the can 8? by another smear B5 of similar meteors materiall In accordance with one embodiment of the invention, a terminal 43 is provided forthe'liigh tension end by soldering a piece 86 of metallic foil to the smear 85. She foil, before soldering, may be a disc having a diameter approximately twice as great as that of the vial. After the foil is soldered, the disc isconedor, drawn tit to a peak as shown in Figure 3 so as to readily fit into the chamber 88 together with the second: arv \vinding When the secondary assembly is forced into chamber against the electrode terminal 19 and adapts itself to the contour of the adjacent structure to assure good electrical connection and .efiective mechanical support.

It is to be understood that g v 8d, the foil cone 86 is wadded other means may; if desired, be employed to afford a terminal for the secondary winding For example, a small helical spring may be compressed between the smear 85 and the electrode terminal 19 to provide effective electrical connection and a resilient mechanical support.

NVhen the transformer secondary assembly is mounted in the chamber 80,a low tension termine] or pigtail 42 may be held in contact with the edge 8? ofcasingtl by the connecting cable l2. Alternatively, the transformer secondary assembly may be permanently mounted within the chamber by a solder-ed connection between the low tension terminal at 42 and the edge 81, or by a body of solder bridging the spark plug casing and the smear S4, or by any other suitable anchoring means that may readily occur to one skilled in the art. I

The primary winding 331s adapted to be received in the, glass cup 873 in closely coupled relation to the secondary winding 4}, This primary winding may comprise an elongated substantially cylindrical sleeve or core 88,, Figures ,2 and, 3, which has anaxial bore, for receiving an end of the conductor 38,;together witha base portion 89, a flange 9!! providing a shoulder 9i, and a helical groove 52 in which the wire of the primary winding 39 is received and seated. Any insulating materials may be used for the core which will withstand the high temperatures encountered at the spark plugs without gassing, such, for example, glass Micalex or Bakelite after treatment for about twenty-four. hours at a temperature of about 150 C.

The conductor 33 may be anchored in the core 8E! by an end plate or washer 93 and connected to the adjacent end of the primary winding 35?. For this purpose, the end of the primary winding may be drawn through a slot 94 in the core 88 and soldered to conductor 38 at the timethe washer 53 is soldered thereto for anchorage. I he other end of the primary, 39 may eXtend through a passage in the base portion as to serve as a terminal for connection to the conductor Ml.

; sleeve separating insulation is used.

its previously pointed out, the transformer structure is thoroughly impregnated, after assembly, with a suitable insulating compound to avoid coronaeffect and attendant energy loss. A body of such impregnating compound is indicated at 96. The transformer windings may be held within the chamber 80 in the spark plug casing 3! by an internally threaded sleeve nut 93 which engage the threaded portion 82. The nut 91 may have a flange 93 which is seated on a flange 59 formed on a sleeve lilil, an internal shoulder in the sleeve led bearing against the core shoulder Si. The outer edge of the sleeve R 0 is thus held in contact with the edge'lll of the spark plug casing 3! to clamp, if desired, the secondary terminal at 52 therebetweenand to aiford a good electrical connection between the casing and the sleeve as at 30.

From the foregoing description, it will be appreciated that a small. compact transformerspark plug unit is obtained which is effectively shielded by the casing iii together with the shielded end portions or" the cable l2 including the nut 9.1 and sleeve tell whereby radio noise disturbances arising from. the high frequency circuits are suppressed or eliminated. This mounting also eliminates long leads between the transformer secondary and the adjacent electrodes whereby energy losses are avoided. The transformer assembly of a typical embodiment of the invention is in overall dimensions about one inch long and about three-eighths of an inch in diameter and has a turn-ratio ofv the order or 15 to 29;; with the secondary winding having about 420 turns of very fine wire; In, conventional transformers where voltage stresses on the insulation separating the primary winding from the secondary winding run as high as 2,000 to 3,660 volts per mil, and may in the case of. localized stresses run possibly as high as 10,000 volts per mil, there is a serious possibility of flash-over between the primary winding, which is substantiallyat ground potential, and the high tension end of the secondary winding if mere The use of the closed-bottom glass cup at in this invention avoids the necessity of providing a long fiashoverpat-h, as by extending a separating tubeor sleeve ,far beyond the high tension'end of the secondary winding. The relatively thin-walled giasscup or vial element of the novel transformer effectively eliminates flash-over while assuring a structure of minimum dimensions that is capable of efiiciently standing up under such high voltage stresses and the relatively high heat of oper ation without an undue separation, of the two windings, thereby assuring maximum operational efficiency.

In Figure 4 is shown an alternative construction which may be employed for the primary winding 39. This so-called. air-core structure may comprise a cupped metallic member lill hay ing a peripheral flange W2. A plug m3 of suitable insulating material is molded into the cup I0! and extends through a passage in the bottom thereof, with an axially extending conductor or metallic rod I94 fixed therein. The primary winding '39 is disposed about the rod EM with one end seated against the cup E3! and the other end preferably twisted about and soldered to the rod I F s' 'r'eB is shown a modified form of transformer construction and attain mounting thereof. The glass cup ,83 with the secondary winding 4| mounted thereon is secured within the chamber 80 by a metallic ring H9 soldered to the casing within the end flange 81. of. the secondary 4| is also soldered to the ring 19. The core 88 is formed of suitable insulating material which is initially of such resiliency as to permit the wire of the primary to be embedded therein when wound. This primary construction preferably is of a diameter to permit snug socketing thereof into the glass cup 83 during assembly. The escape of excess impregnating compound 96 maybe provided for during assembly of parts in any suitable manner, such as by longitudinally extending ways, to avoid difiiculties which may arise as a result of piston action. Alternatively, piston action may be avoided by tapering both the glass cup 83 and thecore 88 as suggested in Figure 6.

.. The operation of the device of the present in vention willbe more readily understood by reference to the circuit diagram shown in Figure 1. The magneto successively delivers pulses of current having a peak voltage of about 1,000 to 1,500 volts through the distributor to the various supply circuits Iii-24, each of which includes, as a part of the converter unit l4, the condenser which is thus charged. The condenser 35, spark gap 36 and transformer primary winding 39 are connected in series to provide a high frequency oscillatory circuit which is excited by the pulse impressed on condenser 35. The peak voltage of the high frequency oscillations is stepped up to in excess of 30,000 volts by the transformer with the result that high frequency sparks are created at the gaps between the spark plug electrodes 44 and 32, which efiiciently fire charges of fuel even though the spark plug electrodes be fouled with carbon or oil. It will thus be seen that the objects set forth above, among others, are efficiently attained and since certain changes may be made in the above construction and difierent embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

'It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

I Wliat is claimed as new and desired to be secured by Letters Patent is:

1,.A transformer-spark plug comprising, in combination, a spark plug structure including a netalliccasing having a chamber therein, a pair of electrodes mounted on the spark plug, a transformer secondary winding structure mounted in said chamber including a cup of insulating material and a secondary winding wound around the exterior of said cup, the ends of said winding being'connected, respectively, to said electrodes, and'atransformer primary winding mounted in aid r n- V .e

2. 'A'; transformer-spark plug comprising, in c' mbination, a spark 'plug structure including a metallic casing havinga chamber therein, a pair of electrodes mounted-on the spark plug, a transformer secondary winding structure mounted in nidchambger includin a cup of insulating mate'- rial and asewndary winding wound aroundthe The low tension end exterior of said cup, the high tension end of said winding being connected to one of said electrodes, the low tension end of said winding being connected through the casing to the other of said electrodes, and a transformer mounted in said cup.

3. A transformer spark plug comprising, in combination, a conventional spark plug structure includinga metallic casing having a circuit connector chambertherein and a central electrode terminal exposed in the bottom of the chamber, a transformer secondary winding structure mounted in the chamber and including a cup of insulating material and a secondary winding wound about the exterior of said cup with the end of the winding adjacent the cup bottom being in electrical connection with said terminal and the other end being in electrical connection with said casing, and a transformer primary winding mounted in said cup.

4;. A transformer spark plug comprising, in combination, a spark plug structure including a metallic casing having a circuit connector chamber therein and a central electrode terminal exposed in the bottom of the chamber, a transformer secondary winding structure mounted in the chamber including a glass cup and a secondary winding wound about the exterior of said cup with the end of the winding adjacent the cup bottom being in electrical connection with said terminal and the other end being in electrical connection with said casing, and a transformer primary winding mounted in said cup.

5. A transformer-spark plug comprising, in combination, a spark plug structure including a metallic casing having a circuit connector chamber therein and a central electrode terminal exposed in the bottom of the chamber, a transformer secondary winding structure mounted in primary winding the chamber including a cup of insulating material and a secondary winding wound about the exterior of said cup with the end of the winding adjacent the cup bottom bein in electrical connection with said terminal and the other end being in electrical connection with said casing, and a transformer primary winding removably socketed in said cup.

6. A transformer-spark plug comprising, in combination, a spark plug structure including a metallic casing having a circuit connector chamber therein and a central electrode terminal exposed in the bottom of the chamber, and a transformer secondary winding structure mounted in the chamber including a cup of insulating material and. a secondary winding wound about the exterior of said cup with the end of the winding adjacent the cup bottom being in electrical connection with said terminal and the other end being in electrical connection with said casing.

7. A transformer-spark plug comprising, in combination, a spark plug structure including a metallic casing having a circuit connector chamber therein and a central electrode terminal exposed in the bottom of the chamber, and a transformer secondary winding structure mounted in the chamber including a cup of insulating material and a secondary winding wound about the exterior of said cup with the end of the windingadjacent the cup bottom being in electrical connection with said terminal and the other end being in electrical connection with said casing, the exterior or" said casing being threaded for removable anchorage thereto of a connecting cable having a transformer primary winding thereon adapted to be socketed in said cup.

8. A transformer-spark plug comprising, in combination, a spark plug structure including a metallic casing having a circuit connector chamber minal exposed in the bottom of the chamber, and a transformer secondary winding structure therein and a central electrode termounted in the chamber including a glass cup 7 and a secondary winding wound about the exterior of said cup with the end of the winding adjacent the cup bottom being in electrical conbeing in electrical connection with said terminal 2 and the other end being in electrical connection with said casing, a transformer primary winding mounted in said cup, and bodies of a relatively 10 heat-stable compound impregnating the interior of said cup.

10. A transformer-spark plug comprising, in combination, a spark plug structure including a metallic casing having a circuit connector chamber bounded by walls of insulating material and a central electrode terminal exposed in the bottom of the chamber, a transformer secondary winding structure mounted in the chamber including a glass cup and a secondary winding wound about the exterior of said cup, awadded piece of metallicjfoil anchored to the bottom of said cup in electrical connection with the high tension end of said winding and in contact with said terminal, and means grounding the other end of said winding to said casing.

ALEXANDER C. WALL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 5 Number Name Date 2,266,614 Robinson Dec. 16, 1941 2,378,893 Berkey June 26, 1945 2,392,171

Marsh Jan. 1, 1946 

